The more irradiation a PV module absorbs, the higher the electricity yield generated by the system. The glass of today`s modules is therefore already manufactured in such a way that as little light as possible is reflected from the surface.
This is made possible by an anti-reflective coating (ARC), which has been used in the production of solar glass for about 10 years. This increases the entry of sunlight on the solar cell and thus also the yield with the same irradiation. However, solar modules that are more than a decade old were usually produced without anti-reflective coated glass and thus have a lower efficiency.
To make the advantage of an anti-reflective coating available to owners of older solar parks, Covestro, the market leader in coatings, has established a turnkey service. The integrated PV specialist greentech is the execution partner and organises both the required cleaning of the modules and the application of the subsequent anti-reflective coating on the already installed modules in the field and ensures the desired quality of the application. The two companies have already been cooperating for more than two years to help existing installations achieve higher yields.
“We are pleased to be entering our third season together with Covestro and to be able to improve the performance of older plants with this service,” says greentech Managing Director Jörn Carstensen. For the execution of the orders, greentech works closely with the company Planung & Anlagentechnik by Thomas Martin. As an experienced, TÜV-certified solar cleaner, Martin and his team take care of the cleaning and subsequent anti-reflective coating of the modules. His experience in the field has also been incorporated into the optimisation of the technology for applying the coating.
Yield increase up to 4 % possible
Covestro is considered the market leader for anti-reflective coatings in the industrial production of PV and solar glass. The reason for this is a unique technology approach that has already been used in glass factories worldwide since 2011. “In a conventional light incidence, around 4 % to 8 % of the sunlight hitting a PV module is reflected. The maximum transmission gain of a single-layer nanoporous AR coating under perpendicular light is just over 3 %. In addition, there is an angular effect under outdoor conditions that can add another 1 %, so the total gain at outdoor conditions can add up to about 4 %,” says Jörn Brembach, Commercial Manager Europe at Covestro.
In 2018, the company presented its further development for the retrofitting of existing PV systems. “Depending on the general conditions, yield increases of between 2 % and 4 % can be realised with our service,” promises Brembach. Thus, even with an additional yield of 2.5 % per year and a solar park size of 10 MWp with a feed-in-tariff of 0.35 €/kWh, additional revenues of about 90,000 € per year are realistic. Convinced of the quality of the product, Covestro even provides a money-back guarantee for the project price and extended product liability for its portfolio customers for the period of 5 years.
Covestro verifies the effectiveness of its retrofitted anti-reflective coating through regular optical or electrical before-and-after data analysis. The optical analysis is carried out on a regular basis at the solar park using specially developed measuring equipment. Monitoring data provided by the plant is also evaluated. This provides the customer with transparent and comprehensible proof of the actual success of the measure.
Implementation during ongoing operation and turnkey from a single source
To date, greentech and Covestro have already jointly retrofitted more than a dozen solar parks with well over half a million square metres of module surface. The retrofit AR coating is applied by means of a spray process. After an evaporation period of a few seconds, the coating, which is based on silicon dioxide (the main component of glass), has an internal porosity but leaves a closed and smooth surface indistinguishable from the original glass underneath. The coating is very durable and can be professionally cleaned on a regular basis. The application process is proven harmless to the surrounding ecosystem.
greentech and Covestro worked together for a long time on the practical implementation in the solar park. The industrial spray beam, which was specially developed for the carrier vehicles, ensures an even application of the substance, which is only about 100nm thin, directly in the field and close to the module. At the same time, it also allows work on uneven terrain or soft surfaces. “This enables us to coat around 2.5 MWp of PV modules per day without interrupting plant operation,” explains greentech Managing Director Carstensen. “Through further process optimisations, we expect to become even faster in 2022, so that we can also coat larger plants in the shortest possible time.”
The approach implemented by the companies makes it possible to offer the coating and the module cleaning required beforehand from a single source. This offers organisational advantages and saves time and coordination effort.
The basic prerequisite for the implementation of a retrofit coating is certain general conditions on the system: For this purpose, an inspection to check the suitability of the system takes place in advance on site and free of charge for the customer. For example, the module rows should have a certain distance to ensure that the carrier vehicles and equipment can drive within the solar farm. In addition, the remaining service life of the system must be considered for the economic consideration, says Carstensen: “Of course, there are certain costs involved for the coating. As a rule, these pay off during a period of about 2-3 years. This represents a very attractive re-investment case for the plant owners and prepares the solar plants for the time after the subsidy period.”
Are you interested in a retrofit coating for your existing system and would like more information? Please contact us!
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